Reference is made to commonly assigned co-pending U.S. patent application Ser. No. 09/748,620 filed Dec. 22, 2000, entitled: HYBRID CAMERA FILL-FLASH, and filed in the names of Hirohiko Ina and Hisanori Hoshikawa; Ser. No. 09/747,664 filed Dec. 22, 2000, entitled: COLOR CORRECTING FLASH APPARATUS, CAMERA, AND METHOD, and filed in the name of David L. Funston; Ser. No. 09/748,668 filed Dec. 22, 2000, entitled: CAMERA HAVING VERIFICATION DISPLAY WITH VIEWER ADAPTION COMPENSATION FOR REFERENCE ILLUMINANTS AND METHOD, and filed in the names of David L. Funston and Kenneth A. Parulski; Ser. No. 09/748,668 filed Dec. 22, 2000, entitled: CAMERA HAVING VERIFICATION DISPLAY AND WHITE-COMPENSATOR AND IMAGING METHOD, and filed in the name of Kenneth A. Parulski; Ser. No. 09/748,100 filed Dec. 22, 2000, entitled: CAMERA HAVING USER INTERFACE WITH VERIFICATION DISPLAY AND COLOR CAST INDICATOR, and filed in the names of David L. Funston, Kenneth A. Parulski, and Robert Luke Walker; Ser. No. 09/748,667 filed Dec. 22, 2000, entitled: CAMERA HAVING VERIFICATION DISPLAY WITH REVERSE WHITE BALANCED VIEWER ADAPTION COMPENSATION AND METHOD, and filed in the names of Kenneth A. Parulski and David L. Funston; Ser. No. 09/748,664 filed Dec. 22, 2000, entitled: CAMERA HAVING USING INTERFACE AMBIENT SENSOR VIEWER ADAPTION COMPENSATION AND METHOD, and filed in the name of Kenneth A. Parulski; and Ser. No. 08/970,327 filed Nov. 14, 1997, and filed in the names of James R. Niederbaumer and Michael Eugene Miller.
The invention relates to photography and photographic equipment and more particularly relates to photography and photographic equipment and more particularly relates to a camera having a user interface including a verification display and a color cast indicator and related method.
Some hybrid film capture-electronic capture cameras capture an electronic image when a film image is captured and show the electronic image, on a display as a verification image that indicates what was captured in the film image. It is desirable that the verification image present enough information for the user to decide whether to take corrective action, such as making another exposure of the same subject, under different conditions, to replace the earlier exposure.
The color balance of captured images is of particular interest to a photographer using a camera that provides a verification image, since many color balance problems can be readily corrected in a second exposure under different lighting conditions, such as flash illumination or outdoors. The color balance of latent photographic images depends on the spectral power distribution, that is, the color temperature, of the scene illuminant. The term xe2x80x9ccolor temperaturexe2x80x9d and like terms are used herein in a sense that encompasses both actual color temperatures and correlated color temperatures. The definition of xe2x80x9ccorrelated color temperaturexe2x80x9d in The Focal Encyclopedia of Photography, 3rd ed., Stroebel, L. and Zakia, R., ed., Focal Press, Boston, 1993, page 175, states:
xe2x80x9cCORRELATED COLOR TEMPERATURE A value assigned to a light source that does not approximate a black body source and therefore does not possess a color temperature. The correlated color temperature is the color temperature of the blackbody source that most closely approximates the color quality of the source in question. Correlated color temperatures are determined by illuminating selected color samples with the source in question and then determining the color temperature of the blackbody source that results in the color samples appearing the most similar to a standard observer.xe2x80x9dThe color balance of latent photographic images also depends on the type of film used. A film of a given type is formulated to provide a neutral response to a particular designated illuminant. A neutral response matches the spectral power distribution of the designated illuminant. For example, xe2x80x9cdaylightxe2x80x9d film directly exposed by daylight records equal printing densities for each of the cyan, yellow, and magenta film records. A resulting photographic print, photofinished so as to maintain the neutral response, will be properly color balanced with white objects in the scene appearing as white objects in the printed image.
If a film of a given type is exposed using an illuminant that has a different color balance than the designated illuminant for that film type, then the resulting final images will have a color cast, that is, a non-neutral response in the form of a color balance shift that causes white objects in the scene to appear colored. For example, a color cast in a photographic print means that white objects in the scene are reproduced at a noticeably different correlated color temperature than that of a xe2x80x9cwhitexe2x80x9d illuminant used to illuminate the print. The color cast can be described in terms of the perceived color that replaces white. With daylight film, fluorescent exposures printed neutrally (that is, with the same printed balance as used for daylight exposures) result in images having a greenish color cast when viewed in daylight; tungsten exposures have a reddish-orange color cast.
The color balance of a final photographic image produced by photofinishing also depends upon the scene balance algorithm used to control the photographic printer or other photofinishing equipment used. Many commercially available photofinishing systems attempt to determine the color balance of photographic images before printing to allow compensation for a color cast caused by fluorescent (and tungsten) illumination. The compensation is typically only partial, because partial compensation does not unacceptably degrade highly-colored images (for example, images of bright yellow objects under daylight illumination) that are erroneously judged as having a different illuminant and selected for color compensation. A noticeable color cast is still perceived in the final images, after the partial compensation. Stating this another way, after partial compensation, white objects in the scene shown in final photofinished images are perceived as being non-white in color. This color cast can provide an artistic effect, but in most cases, the remaining color cast is objectionable to the user.
In some digital still and video cameras, this problem with color cast is not present, since the final image is produced from a saved image data set that has been subjected to white balancing. Such images have a neutral color balance when output to an appropriately configured output device. Methods for calibrating to particular devices and media are well known. Many white balancing procedures are known. For example, one method of white balancing is described in U.S. Pat. No. 5,659,357, xe2x80x9cAuto white adjusting devicexe2x80x9d, to Miyano. The result of this process is that the red (R) and blue (B) code values of the digital images captured using various illuminants are scaled by appropriate white balance correction parameters. These parameters are determined such that the white balance corrected R and B codes are approximately equal to the green (G) codes for white and neutral gray objects of the scene.
The human visual system, under common lighting conditions, adapts to illuminants having different color temperatures, in a manner that is similar to the white balancing just discussed. (The terms xe2x80x9cvisual adaptationxe2x80x9d and xe2x80x9cadaptationxe2x80x9d are used herein in the sense of chromatic adaptation. Brightness adaptation is only included to the extent that brightness effects influence chromatic adaptation.) The result is that daylight, fluorescent, tungsten, and some other illuminants, in isolation, are all perceived as white illumination. As noted above, photographic film does not function in the same manner as the human visual system; and after photofinishing, pictures photographed in some lighting conditions are perceived as having a color cast. The viewer perceives the pictures, as if through a colored filter.
A photographer using a hybrid film capture-electronic capture camera, is ordinarily adapted to the ambient illumination. Thus, if a verification image captured under fluorescent illumination is presented to the user without a change in the color balance, then the verification image will match the photographer""s visual adaptation. A white shirt will look white to the photographer, whether viewed directly or in the verification image. The problem with this approach is that what the photographer sees in the verification image does not look like what the photographer will see in the final printed image after photofinishing. White balancing the verification image would not help, since the film image will not balanced the same way in photofinishing. The photographer is also still adapted to the ambient illumination.
U.S. patent application Ser. No. 08/970,327, filed by Miller, M. et al., entitled, xe2x80x9cAutomatic Luminance and Contrast Adjustment for Display Devicexe2x80x9d, which is commonly assigned with this application; teaches a camera which measures the ambient light level and adjusts the brightness and contrast of an image display on the camera.
It would thus be desirable to provide a camera and method providing an indication of the color cast of a captured image to a photographer along with a verification image.
The invention is defined by the claims. The invention, in its broader aspects, provides a camera and method usable for capturing multicolor images of multicolor scenes. The camera has a color detector determining from the multicolor scene and/or a captured multicolor image of the scene, a predominant color in the captured image and/or multicolor scene. The camera also has a display showing a predominant color determined by the color detector, whereby one is alerted to color predominance. for use in capturing images of scenes illuminated by ambient light. The camera has a body and an electronic imager disposed in the body. The electronic imager captures an ambient light image as a multicolor electronic image. A color detector is disposed in the body. The color detector measures the ambient light to provide a color value. A user interface disposed on the outside of said body, shows the electronic image and an indication of the color value. The indication is independent of the color balance of the electronic image.
It is an advantageous effect of at least some of the embodiments of the invention that a camera and method provide an indication of the color cast of a captured image to a photographer along with a verification image.